Fixtures, Faucets, and Appliances
Domain overview
Fixtures, Faucets, and Appliances covers the installation and connection of sinks, lavatories, water closets, showers, bathtubs, floor drains, dishwashers, washing machines, water heaters, and similar equipment. The exam tests fixture clearances, trap seals, trap-arm limits, backflow protection, and appliance connections.
Core rules
- Each fixture that discharges to the drainage system needs a trap with a water seal of 2 to 4 inches, and no fixture may be double-trapped.
- The trap arm runs from the trap weir to the vent. Its maximum length depends on pipe size; a common UPC table limit for 1-1/2 inch is 6 feet.
- Fixtures must be accessible for cleaning and repair, and floor drains need a trap primer where the trap can evaporate.
- Water closets need the code clearance from centerline to sidewalls and in front of the bowl; shower and tub valves need access and anti-scald protection.
- Appliances such as dishwashers and washing machines need an air gap or backflow preventer, and the discharge must not create a cross-connection.
Worked example
A lavatory has a 1-1/2 inch trap and the vent is 7 feet from the trap weir. The trap arm limit is 6 feet for that size, so the installation fails even though the drain slopes correctly. The fix is to move the vent closer, increase the trap-arm size only if the code table allows it, or install an approved air admittance valve where permitted. The reasoning is that a long trap arm can self-siphon and lose the seal.
Traps
Confusing trap-arm length with the total drain length is a common error. Another is using a dishwasher hose tied high without an air gap. Do not install a trap below a fixture without a vent. Do not block the access panel for a tub valve.